1. Chapter 8.1: The mammalian cardiovascular system

2. How does the circulatory system of a mammal differ from a fish, and what effects might this have on its metabolism?
Suggest a list of essential features of a mammalian transport system.

3. Cardiovascular system
Made up of a pump (heart) and system of interconnecting tubes (blood vessels)
Closed system: blood always remains within vessels

4. Blood circulation
Blood travels twice through the heart to complete one “circuit” through the body, known as double circulation
Systemic circulation: oxygen-rich blood circulation throughout body
Pulmonary circulation: oxygen deficient blood circulation between the lungs

5. The mammalian heart

6. Systemic circulation
Oxygen-rich blood is pumped out of the left atrium via the left atrioventricular valve (aka bicuspid or mitral valve) into the left ventricle
It is pumped into the aorta via the aortic semilunar valve (aka aortic valve) and travels to all parts of the body
Returns to the right side of the heart via the vena cava

7. Pulmonary circulation
Oxygen-deficient blood is returned to right atrium via the vena cava
Pumped into right ventricle via the right atrioventricular valve (aka tricuspid valve)
Pumped through pulmonary artery via the right semilunar valve (aka pulmonary valve)

8. Blood vessels
Arteries: always carry blood AWAY from the heart (can be oxygenated/deoxygenated)
Veins: always carry blood TOWARDS the heart (can be oxygenated/deoxygenated)
Capillaries: link systemic arteries to veins. Responsible for carrying blood to individual cells

9. Arteries
Function: transport blood (swiftly at high pressures) to tissues
Walls made up of 3 basic layers: inner endothelium, middle tunica media, outer tunica extrema

10. Endothelium
Inner lining tissue of arteries and veins made up of a layer of flat (squamous epithelium)cells fitting together like a puzzle
Aka tunica intima
Very smooth: minimizes friction with moving blood
Contains elastic fibers

11. Tunica media
Middle layer of veins/arteries containing smooth muscle, collagen, and elastic fibers

12. Tunica externa
Outer layer of veins/arteries containing elastic fibers and collagen

13. Arterial pressure
Blood leaving heart is very high (~120mm Hg or 15kPa during systole)
To withstand such pressure, arterial walls must be very elastic and thick
Arteries have the thickest walls of any blood vessels

14. Arterial pressure
Walls of arteries have high levels of elastic fibers and collagen to allow them to ‘give’ which reduces the chance of them bursting
Blood is pumped in pulses, so arteries are stretched and blood is pumped through them
Closer to the heart= higher pressure & velocity (more elastic fibers)
Farther from the heart = lower pressure & velocity (more muscle fibers)

15. Arterial pressure Arteries expand and contract to normalize pressure
Expand = reduce pressure
Contract = increase pressure
Not 100% effective - feel your radial (wrist) or carotid (neck) artery. You can feel the pulses from your heart expanding and contracting these arteries

16. Arterioles
As arteries reach their transport tissues, they narrow into arterioles
Similar in composition to arteries, but higher % of smooth muscle
Controls volume of blood flowing to a tissue at a given time by expanding/contracting

17. Capillaries
Arterioles continue to branch into the smallest of all blood vessels: capillaries
Capillaries function to take blood as close as possible to all cells, allowing rapid transfer of substances between cells and blood
Oxygen, nutrients, waste, carbon dioxide

18. Capillaries
Form networks called capillary beds in all body tissues, except the cornea and cartilage
hence these tissues will not bleed
Your cornea gets oxygen directly from the air

19. capillaries
Small size allows them to bring blood as close as possible to cells in the body
Capillaries ~7μm in diameter (same size as red blood cell)
Walls are made of single layer of endothelial cells

20. capillaries
Cells in endothelium most often have tiny gaps between them which allow certain components of blood to seep through to body tissues
Blood pressure drops immensely across capillaries (~ 33 mmHg)

21. Veins
As blood leaves capillary beds, capillaries gradually re-join with each other, forming larger vessels called venules
Venules join to form veins
The function of veins is to return blood to the heart

22. veins Typical venous blood pressure is ~5 mmHg or less
This very low pressure means veins don’t need to have as thick walls as arteries
Veins have the same 3 layers, but tunica media is much smaller and there are less elastic fibers

23. veins
Since veins are very low pressure, they need assistance from your skeletal muscles to return blood to the heart
Veins lie very close to muscle (particularly in lower extremities) so when these muscle contract, the increased pressure pushes venous blood to the heart

24. veins
In addition to skeletal muscle help, veins also contain semilunar valves that prevent the backflow of blood in veins
Formed from specialized endothelium tissue

25. Blood pressure through cardiac cycle

26. This is a contrast x-ray of the kidneys and the mighty aorta.